Update cache key creation to use date suffix

.github/workflows/documentation.yml

@@ -46,11 +46,14 @@ jobs:
         with:
           python-version: ${{ env.PYTHON_VERSION }}
 
+      - name: Set the date environmental variable
+        run: echo "cache_id=$(date --utc '+%V')" >> $GITHUB_ENV
+
       - name: Set up build cache
         uses: actions/cache@v3
         id: cache
         with:
-          key: mkdocs-material-${{ github.ref }}
+          key: mkdocs-material-${{ env.cache_id }}
           path: .cache
           restore-keys: |
             mkdocs-material-